The invention relates to a method for carrying out a work operation on a workpiece continually moving forward on a conveying device by an industrial robot moving along with the workpiece. The invention further relates to a device for carrying out such a method.
For the series production of workpieces, essentially two basic concepts exist. With synchronized manufacture, the workpieces to be processed are moved between work stations by a conveying device and are processed there in a standstill state. This is problematic with production lines with a plurality of processing stations, as the synchronization of the further movement of the workpieces between the work station depends ultimately on the work station with the longest processing duration. This results in faster work stations not being able to work at full capacity. Also, workpiece stores or buffer zones may have to be erected, which makes the manufacture more costly.
A continual, conveyor-synchronous processing of the workpiece is thus preferred. The processing of the workpiece takes place here, while the workpiece moves along on the conveying device. Today, conveyor-synchronous manufacturing methods are used predominantly, when workpieces are processed by human workers. A continuous conveyor-synchronous processing over an entire manufacturing line is thereby the exception. Automated processing steps, in particular those which are carried out by industrial robots are at present ill-suited for a conveyor-synchronous operation. These processing steps are thus usually carried out in a synchronous operation, which leads to additional problems with a change between synchronous and conveyor-synchronous sections of a manufacturing line. It is thus desirable to provide methods which permit carrying out robotic working steps in a conveyor-synchronous operation.
DE 103 13 463 B3 discloses a method as described above. An industrial robot is thereby moved along on a separate guide parallel to a conveying device carrying the workpiece. In order to balance position inexactnesses between the industrial robot and the workpiece, the subframe of the industrial robot is thereby coupled to a workpiece carrier. Position inexactnesses between the workpiece and the workpiece carrier are sensed at the start of the method by measuring in a stationary measuring device and are guided to the industrial robot control. In order to ensure the necessary position exactness, however, elaborate coupling devices between the subframe of the industrial robot and the workpiece are necessary. There is practically no play here for tolerances, as the measuring process takes place prior to the coupling.
The present invention provides a method and a device for carrying out a work operation on a workpiece moving forward synchronously with an industrial robot, which overcomes the mentioned disadvantages of the state of the art. A high position exactness between the industrial robot, the workpiece and the workpiece carrier shall be ensured in particular.
According to the present invention, the workpiece is moved along continually on a conveying device. The industrial robot is moved along next to the conveying device along a parallel separate longitudinal guide, wherein a base part of the industrial robot is rigidly coupled to a workpiece carrier during the common run-through of the processing path. In order to decouple the movement of the industrial robot from tolerances of the longitudinal guide, it is mounted in a floating manner with regard to a bogie running in the longitudinal guide. According to the invention, the industrial robot has an exchangeable tool. At the beginning of the common run-through of the work path, a scanner tool or a measuring head is first connected to a working arm of the industrial robot and a relative position between the workpiece and the workpiece carrier is determined by means of the scanner tool. The exact coordinates of the workpiece in the basic coordinate system of the industrial robot are known thereby in an advantageous manner. Tolerances regarding the coupling of the base part of the industrial robot to the workpiece carrier are thus balanced at the same time by the measurement. Thus, coupling devices are used between the base part of the industrial robot and the workpiece carrier that have higher tolerances than known from the state of the art.
After the measuring process, the scanner tool or the measuring head is exchanged for a processing tool. In particular, a processing tool for applying a hollow space conversation to the workpiece may be used. In order to carry out this exchange in a quick and efficient manner, it is thereby advantageous to provide a quick tool change device and a tool store.
By measuring the relative position of the workpiece, the workpiece carrier and the industrial robot, a coupling device may be used for the rigid coupling of the base part of the industrial robot to the workpiece carrier that is designed in a simple manner. In a further arrangement of the invention, a clamping cylinder is provided, which clamps the base part to a longitudinal bar of the workpiece carrier. The at least one clamping cylinder is thereby arranged on a feed plate that is connected to the base part in a movable manner in an exemplary embodiment of the invention.
The feed plate is moved in such a manner for the rigid coupling of the base part to the workpiece carrier, that a stop element arranged thereon comes into abutment with a corresponding element of the workpiece carrier, before the clamping cylinder is clamped to the longitudinal bar. Thus, the starting position of the industrial robot with regard to the workpiece carrier does not have to be kept absolutely precisely in an advantageous manner, in order to bring the coupling device into the desired coupling position. Rather, the exact positioning is generated by the movement of the feed plate. Tolerances resulting thereby can again be balanced by the measuring process by means of the measuring head.
After the rigid coupling of the base part to the workpiece carrier, a drive of the bogie of the industrial robot is decoupled in a further arrangement of the invention. The drive energy for the movement of the industrial robot by the work path is thus completely provided by the conveying device. This reduces the wear of the bogie compared to the methods known from the state of the art, where an active drive of the bogie is also used during the common run-through of the work path. In order to balance speed tolerances between the bogie and the conveying device, a slip coupling has to be provided with an active drive of the bogie, which has a high wear. This can be omitted in the present invention. Since no relative movement takes place between the industrial robot and the workpiece, the drag distance is also equal to zero.
Furthermore, the industrial robot follows all movements of the workpiece in all spatial directions with the method according to the invention, such as in the vertical direction by the weight balance in the vertical direction. No constraining forces result between the industrial robot and the workpiece in this manner, so that the danger of damage to the workpiece or disturbance of the manufacturing process is minimized.
The invention further relates to a device for carrying out a work operation at a workpiece moved along continually on a conveying device by an industrial robot moved along with the workpiece during a common run-through of a work path. The industrial robot can thereby be displaced on a separate longitudinal guide running next to the conveying device. The base part of the industrial robot can be coupled rigidly to a workpiece carrier during the common run-through, wherein bearing elements are provided, via which the base part can be mounted in a floating manner with regard to a bogie that can be moved along in the longitudinal guide. These bearing elements can be, for example, air spring bellows or the like.
According to an exemplary embodiment of the invention, the industrial robot has a tool exchange device with a tool store and a tool holder. At least two different tools can thereby be connected to a working arm of the industrial robot by means of the tool holder. A scanner device or a measuring head for measuring a relative position between the workpiece carrier and the workpiece can be connected to the working arm of the industrial robot. Furthermore, processing tools are provided, whereby one processing tool for applying a hollow space conservation to the workpiece can be connected to the working arm of the industrial robot. A measurement of the relative position of workpiece, workpiece carrier and industrial robot is thereby advantageously enabled directly in the coordinate system of the industrial robot.
In a further arrangement, at least one clamping cylinder is provided, by means of which the base part of the industrial robot can be coupled rigidly to a longitudinal bar of the workpiece carrier. This may be arranged on a feed plate, which is mounted in a displaceable manner with regard to the base part. The clamping cylinder can be moved into a required position with regard to the workpiece carrier by means of the feed plate. The access of the required position for coupling the base part of the industrial robot to the workpiece carrier thus does not have to be carried out by an exact positioning of the bogie of the industrial robot in the longitudinal guide, but the movement of the feed plate is eased considerably.
A stop element is provided at the feed plate in a further arrangement. The stop element can be brought into abutment with a corresponding element of the workpiece carrier for determining the required position.
A coupling is provided in a further embodiment, by means of which a drive unit of the bogie can be coupled to a drive wheel of the bogie. It is thereby possible to drive the industrial robot into a required position in a working phase before the rigid coupling to the workpiece carrier with its own drive. The coupling can be coupled out after the coupling to the workpiece carrier, so that the movement energy of the industrial robot is provided by the conveying device. After the end of the common run-through of the working path, the industrial robot can again be released from the workpiece carrier. At this time, the mentioned coupling can again be coupled in, so that the industrial robot can return into its starting position with its own drive.